R Caffin Style "external frame" by modifying an off the shelf "internal frame" rucsac ?
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Alan Bradley
(ahbradley)
R Caffin Style "external frame" by modifying an off the shelf "internal frame" rucsac ? on 08/01/2011 14:38:03 MDT Print View

Roger Caffin's external frame (no load transferred thru a hip-belt) ruc-sacs look nice, but require MYOG from scratch:

I wondered if the same effect (of a simple H frame with lots of padding) could be gained
by taking a simple standard "internal frame" ruc-sac, the kind with a pouch for sleep mat/frame, and placing a completely rigid frame in this pouch(the H frame), then, in same pouch, in front of this (i.e between said frame and ruc-sac back panel, i.e. between frame and wearers back). The foam (and fabric back panel) would conform to the users back shape, and so "hook" the load onto their back like a proper H frame: hopefully...

Alan Bradley
(ahbradley)
Source on 08/04/2011 06:51:33 MDT Print View

The design I would like a simpler/easier way to replicate...

http://bushwalking.org.au/FAQ/DIY_RNCPacks.htm

http://bushwalking.org.au/FAQ/FAQ_Packs.htm#Theory

Alan Bradley
(ahbradley)
Or could use a child carrier on 08/05/2011 13:49:37 MDT Print View

Or, I think child carrying backpacks are essentially external framed devices, so perhaps one of these would be a head start to a Roger Caffin style external/H frame rucsac, avoiding a load direct to hip joints.

Edited by ahbradley on 08/05/2011 13:55:36 MDT.

Samuel C. Farrington
(scfhome) - M

Locale: Chocorua NH, USA
lightest pack frames on 08/05/2011 14:15:39 MDT Print View

If the pack frame will not be load bearing, consider the best of the frameless or non-load bearing frame packs currently reviewed here.

If it will be load bearing, it is hard to get around the fact that construction material under 3/8" in diameter weighs much less than the larger diameter alu alloy tubing that has been used on most marketed packs and rucksacks. Even solid quarter inch FG rods are much lighter than the larger diameter alloy, as are the thick walled hollow FG tubes used for cheap tents; but FG will not hold a bend like alloy, of course, and the frame design must address that.

For the above reasons, lighter and lower diameter frame material is probably the only way forward, to achieve an SUL load bearing frame.

(Note that the "FSD Edge Connectors" in the 8mm (.312") size from Goodwinds might make great T connectors to replace the home-made ones crafted by Roger. They are friction fit, so require no adhesive or fasteners. The challenge is putting a slight uniform bend in the 8mm alloy tubing, without Roger's "rolling jenny" device. Tried a Ridgid 3/8" tube bender, but it leaves small crimps on the inside of the bend as you go along, bending just a little at successive points, which weakens the tubing.)

Will post on completion of current project using mostly 1/4" dia. FG and 8mm Easton .340" dia. alloy, and even small lengths of 1/4" solid alu (for two very low radius bends). The FG rod was chosen over carbon fiber, because it is much more flexible, still very strong, and not that much heavier for the same dia.(also much cheaper). The frame will be integral to the pack, and have sidearms to eliminate the full waist belt, a la Jack Stephenson's original go-pack, which used an additional connection to the hip belt at the small of the back to avoid the backward pull of the sidearm frames that have beoome obsolete.

I used an MYOG go-pack design for many years, and still find it much more comfortable than anything with a full waistbelt, and that includes for loads in the 20-30 lb. range. The challenge is to greatly reduce the weight of the frame structure, including foldable sidearms. Without that, no amount of pricey cutting edge fabric will achieve the lightest pack weight. When carrying a much lighter pack, the bomb proof constructed frames I used to make should not be needed.

Good luck to us both.

Samuel C. Farrington
(scfhome) - M

Locale: Chocorua NH, USA
"R Caffin Style "external frame" by modifying an off the shelf "internal frame" rucsac ?" on 08/09/2011 20:38:18 MDT Print View

Forgive posting on my post, but must confess a change of mind. Ordered some carbon rods and fittings to use instead of FG for the new pack. The weight savings were too tempting, and the stiffer carbon should function much better to keep a suspended mesh back panel taut.